Process of making a red vat-dyeing dye.



UNITED STATES PATENT OFFICE.

GADIENT ENGI, OF BASEL, SWITZERLAND, ASSIGNOR TO FIRM OF SOCIETY OF CHEMICAL INDUSTRY IN BASLE, OF BASEL, SWVITZERLANI).

Specification of Letters Patent.

Patented Sept. 25, 1906.

Application filed March 22, 1906. Serial No. 307,409.

(called by Muller phenylthioacetic carboxylic acid,) or"1ts dimethyl ester with caustic-soda lye at a high temperature and subsequently oxidizing with potassium ferricyanid. The dyestu'ff thus obtained may be regarded as having the constitution of indigo, in which sulfur takes the place of the imido groups.

I have found that the dyestuff described by Muller, which is obtainable only in small quantity by the rocedure he prescribes, may be manufactured on a sufficiently large scale for commerce by heating salicylthioacetic acid not with caustic-soda lye, but in presence of an organic solvent or diluent which yields oxygen, such as an aromatic nitrohydrocarbon, the finished dyestufl' being thus obtained in one operation, since it may be separated in a pure form by cooling the mixture. This manufacture forms the subjectmatter of this invention and is illustrated by the following examples:

Example I: Ten parts, by weight, of salicylthioacetic acid are boiled with fifty parts of nitrobenzene in a reflux apparatus, 'where by the solution gradually becomes deep-blue red. The boiling having been continued for about five hours,-the mixture is cooled, and the dyestufl',which has separated in the form of beautiful lustrous brown-red crystals, is filtered and washed with; alcohol to remove the adhering nitrobenzene. In this manner the dyestufl' is obtained in a very pure condition.

Example II: One part, by weight, of the salicylthioacetic acid is heated with one part of a dinitrotoluene and foul-parts of diphenylaminfor three to four hours at 2 10 to 220 centigrade. The cooled mixture is extracted with hot alcohol, whereby the red dyestufl is obtained in a pure condition without further treatment in the form of red-brown needles having alcohol in them.

Instead of the nitro compounds specified in Examples I and II may be used with like result other nitro compounds, such as ortho or para nitrotoluene or dinitrobenzene, and instead of diphenylamin another indifferent solvent may be used without essentially affecting the final result.

The dyestufl' manufactured as described is identical with that produced by G. Muller and when dried is a bluish-red powder which is insoluble in water and cold alcohol. In boiling alcohol it dissolves only slightly to a violet-red solution. In hot benzene it dissolves more freely to a beautiful carmin-red solution having a brilliant yellowish-red fluorescence. The solution in strong sulfuric acid is bluish green, and dilution of the solu tion with water precipitates the unchanged dyestufl as blue-red flocks. The dyestuft' can easily be worked up into a vat with aid of a reducing agent, such as sodium hydrosulfite, and this clear yellow vat dyes cotton without a mordant when applied in a suitable manner, the tint developed on the cotton when it is subsequently exposed .to the air being blue red. 'The dyeings are absolutely fast to washing and to light, and, moreover, are advantageously fast to chlorin.

WVhat I claim is 1. The herein described process for the manufacture of .a red vat-dyeing dyestufl, which consists in heating salicylthioacetic acid S.CH2COOH OBI I4 OOOH in presence of an aromatic .nitrohydrocarbon.

2. The herein-described process for the In Witness whereof I have hereunto signed 10 manufacture of a red vat-dyeing dyestufl, my name, this 8th day of March, 1906, in the which consists inheating salicylthioacetic acid presence of two subscribing Witnesses.

GADIENT ENGI.

(2 )GOOH Witnesses in presence of an aromatic nitrohydrocar- GEO. GIFFORD,

bon with addition of an indifferent solvent. AMAND BITTER. I 

